Offshore wind power generation systems have become more important from a viewpoint of worldwide demand for and economic performance of renewable energy. Above all, it has become more important to achieve the practical use of floating offshore wind power generation systems constructible even in deep sea areas.
As shown in FIG. 11, a conventional floating offshore wind power generation system is anchored to the seabed with three or more mooring members in order to suppress pitch vibrations (windwise vibrations), roll vibrations (across-wind vibrations) and yaw vibrations (rotational vibrations) of a floating body.
However, an offshore construction work for setting up the three or more mooring members substantially with an equal tension lowers the economic performance of the floating offshore wind power generation system. This triggers a strong demand for a floating offshore wind power generation system that is anchored in place with a single mooring member.
As to the floating offshore wind power generation system, a technique such as set forth in Japanese Unexamined Patent Application Publication No. 2005-526213 is known, for example. Japanese Unexamined Patent Application Publication No. 2005-526213 discloses “a wind-driven electric power plant which is built afloat at a deep sea area and includes: a machine room including an electric generator; an adjustment device; a rotor shaft and a rotor blade. The power plant has a structure where the above-described machine room is mounted atop a tower that is anchored to the seabed and basically afloat in an upstanding position because of the gravity center of the whole wind mill located downward from the center of buoyancy of the wind mill”.
According to the wind-driven electric power plant of Japanese Unexamined Patent Application Publication No. 2005-526213, the large floating-type power generating wind mill installed offshore can achieve sufficient stability for absorbing wind power acting on the windmill rotor.